Substantial effort and expense have been devoted to the development of reliable focus and tracking control devices for optical data storage systems, such as optical disk memories. One of the more promising focus control techniques relies on a servo controlled voice coil motor to move a focusing lens forward and back relative to an optical recording medium as necessary to maintain a light beam in sharp focus on the optically sensitive surface (i.e., the information bearing surface) of the recording medium. Tracking, on the other hand, is conventionally performed by a servo controlled galvanometer which causes the focused beam to follow a preselected data track. Unfortunately, such electro-mechanical focus control and tracking devices tend to be somewhat sluggish because of mechanical inertia. Moreover, voice coil driven focusing lenses are quite expensive.
As is known, an optical waveguide may be created by coupling electric fields into an electro-optic element, thereby locally increasing the refractive index of the electro-optic element to produce a waveguiding region therein. See, U.S. Pat. No. 3,795,433, which issued Mar. 5, 1974 on "Voltage Induced Optical Waveguide Means."